(1) Field of the Invention
The present invention relates to the exercise of control over the aiming of an elongated member, particularly a chute for conveying solid material, and to the application of the said control technique to the charging of pressurized shaft furnaces. More specifically, this invention is directed to apparatus for positioning a rotatable and angularly adjustable charge distribution chute mounted within a furnace. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
(2) Description of the Prior Art
While not limited thereto in its utility, the present invention is particularly well suited for use in the delivery of solid charge material to the hearth of a blast furnace wherein high pressures are maintained. Modern blast furnace technology demands that the deposition of the material with which the furnace is charged be accurately controlled. This accurate charge distribution control must be achieved in the face of exceedingly high temperatures and operating pressures. Two basic types of charging devices are presently known in the art. The first, which has been in use for many years, employs superimposed bells of unequal diameter. When employing such bells, it is not possible to introduce the charge in an even and uniform manner over the surface of the furnace hearth. The second category of charging device comprises "bell-less" apparatus which employs a rotatable and angularly adjustable distribution chute located within the furnace. The desired charge profile on the furnace hearth may be obtained through exercise of control over the aiming of this chute as the charge material is supplied to the upper end thereof from a pressurized storage hopper. Such "bell-less" charging installations are shown in U.S. Pat. Nos. 3,693,812, 3,814,403, 3,880,302, 4,042,130, 4,074,816 and 4,153,140.
The presently employed mechanisms which rotate the charge distribution chute and adjust its angle of inclination in the "bell-less" charging installations have portions of the drive apparatus exposed to the exceedingly harsh environment which exists in the furnace throat. In the typical installation, the distribution chute is mounted from a rotatable casing which is positioned concentrically around a central feed channel or spout; the central feed spout being coaxial with the furnace and serving to direct the charge material from a storage hopper or hoppers onto the upper end of the controllable chute. Means in the form of a first mechanical drive train imparts rotary motion to the casing to thereby rotate the distribution chute. A further drive train rotates with the casing and independently drives the chute so as to vary the angular orientation thereof with respect to the furnace vertical axis. The rotatable casing, in part, defines an annular chamber in which is positioned the drive train for controlling the distribution chute angular position. This chamber will be separated, but not hermetically isolated, from the interior of the furnace at its lower end by means of an outwardly extending flange on the rotatable casing and a co-planar flange which extends inwardly from the furnace wall. The distribution chute is coupled to the drive means located within the annular chamber by means of a control rod which passes through an aperture in the flange which extends outwardly from the rotatable casing. In operation, the casing, distribution chute, control rod and the means for driving the control rod rotate together about the common vertical axis of the furnace and feed spout under the influence of the first drive train. During this rotation, through operation of the second drive train, the distribution chute may be caused to pivot about its horizontal suspension axis whereby the charge material failling under the influence of gravity to the furnace hearth may be guided by the chute so as to transcribe, by way of example, concentric circles or a spiral pattern.
Co-pending U.S. patent application Ser. No. 65,289 now Pat. No. 4,273,492, which is assigned to the assignee of the present invention, discloses recent improvements in drive mechanisms and techniques for distribution chutes of "bell-less" shaft furnace charging installations. Co-pending application 65,289 teaches the provision of cooling for the annular chamber containing some of the drive mechanisms for the distribution chute. This cooling was typically previously accomplished by delivering, to the interior of this chamber, an inert cooled gas and also by providing for the flow of a liquid coolant in one or both of the rotatable and stationary flanges which define the lower end of the annular chamber. The said co-pending application 65,289 further discoses a distribution chute inclination angle adjustment mechanism which employs a telescoping control rod. The apparatus of the said co-pending application has, as one particularly desirable attribute, the minimizing of the width, measured radially from the furnace axis, of the annular chamber. This minimization of chamber width reduces the area of the base of the chamber and thus also reduces the heat flow from the interior of the furnace to the chamber. Thus, the cooling requirements for the distribution chute drive are reduced by the apparatus of application 65,289. In fact, employing the apparatus of the co-pending application and providing for coolant flow in the flanges which define the base of the annular chamber, the necessity of delivering gaseous coolant into the chamber is obviated.
A disadvantage with the apparatus of co-pending application 65,289 now U.S. Pat. No. 4,275,492 and other prior "bell-less" charge distribution chute control technique resides in the fact that the major portion of the base of the annular chamber, in which the components of the drive system are located, is defined by the outwardly extending annular disc or flange which is integral with the rotary casing from which the chute is suspended. Thus, in order to provide for liquid cooling of this rotating flange, recourse must be had to rotary joints of large diameter. Use of such rotating fluid couplings, particularly those of large diameter, increases the cost of the apparatus and presents potential leakage problems. It has previously been deemed impractical to effect a significant reduction in the width of the rotary flange in order to increase the area of the stationary flange which, of course, is easier to cool. Considering by way of example the apparatus of co-pending application 65,289, the telescopic element of the control rod must, in order to have sufficient strength, be of comparatively large diameter and this control rod element must pass through an opening provided in the rotary flange. Thus, the dimensions of the control rod impose a limit on the dimensions of the relatively hard to cool rotatable disc or flange, this flange in part defining the base of the annular chamber which houses components of the chute drive.
It is also to be noted that the provision of comparatively complicated articulated suspension devices for the driven end of the control rod, such suspension devices being located in the above-mentioned annular chamber, increases the cost of the overall charging installation. It is always desirable to reduce system complexity and thereby reduce cost and enhance reliability.